1. Field of the Invention
The present invention relates to technologies by which to control the I/O access, and it particularly relates to a technology by which to control the access requests from external devices.
2. Description of the Related Art
Along with recent years' significant advance of the computer graphics technology and image processing techniques, which are utilized in the fields of computer games, digital broadcasting and the like, there is demand that the information processing apparatus such as computers, gaming machines and televisions be equipped with faster processing capacity to process high-definition image data. To meet such demand, it goes without saying that the arithmetic processing itself needs to be done at high speed. By the same token, it is important to suitably distribute the tasks among a plurality of processing units.
Each processing unit accesses memory as appropriate when tasks are to be executed. In so doing, if the access by a processing unit B to a memory area secured for the processing of a processing unit A is granted, the performance stability will be impaired. Particularly in the case of an I/O device for controlling the peripheral equipment, there are many cases where a DMA requestor directly designates a physical address so as to control the memory. The malfunction of such an I/O device or a device driver that controls the I/O device may impose a serious effect on the performance stability of an information processing apparatus.